Industrial process device utilizing piezoelectric transducer

ABSTRACT

A process device for coupling to an industrial process for use in monitoring or controlling the process includes a device housing configured to physically couple to the industrial process. A process variable sensor is configured to measure a process variable and measurement circuitry coupled to the process variable sensor provides an output related to the sensed process variable. A piezoelectric transducer provides an electrical output related to pressure pulsations in the industrial process. Electrical circuitry in the housing includes an input configured to receive the electrical output from the piezoelectric sensor.

BACKGROUND OF THE INVENTION

The present invention relates to industrial process devices of the typeused to couple to industrial process control and monitoring systems.

In industrial settings, control systems are used to monitor and controlinventories of industrial and chemical processes, and the like.Typically, a control system performs these functions using field devicesdistributed at key locations in the industrial process and coupled tothe control circuitry located in a control room by a process controlloop. The term “field device” refers to any device that performs afunction in a distributed control or process monitoring system,including all devices used in the measurement, control and monitoring ofindustrial processes.

Some field devices include a process variable sensor. Typically, thetransducer transforms an input into an output having a different form.Types of transducers include various analytical equipment, pressuresensors, thermistors, thermocouples, strain gauges, flow transmitters,positioners, actuators, solenoids, indicator lights, and others. Otherfield devices include a control element and are used to control theindustrial process. Examples of such process devices include valvecontrollers, valve position controllers, heater controllers, pumpcontrollers, etc.

In many process installations, process devices experience pulsations.The pulsations can occur during normal operation of the process.

SUMMARY

A process device for coupling to an industrial process for use inmonitoring or controlling the process includes a device housingconfigured to physically couple to the industrial process. A processvariable sensor is configured to measure a process variable andmeasurement circuitry coupled to the process variable sensor provides anoutput related to the sensed process variable. A piezoelectrictransducer provides an electrical output related to pressure pulsationsin the industrial process. Electrical circuitry in the housing includesan input configured to receive the electrical output from thepiezoelectric sensor. In one configuration, the electrical outputprovides power to the process device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram of a process monitoring or control systemfor monitoring or controlling an industrial process.

FIG. 2 shows a cutaway view and simplified block diagram of a processdevice including pulsation sensing circuitry for use in performingdiagnostics.

FIG. 3 shows a cutaway view and simplified block diagram of a processdevice including pulsation sensing circuitry for use in generating powerfor the process device.

FIG. 4 is a bottom plan view of a sensor module including an isolationdiaphragm for use with a piezoelectric transducer.

FIG. 5 is cross sectional view showing an isolation diaphragm for usewith a piezoelectric transducer.

FIG. 6 is a planned view of a process device including a piezoelectrictransducer located in a mounting flange.

FIG. 7 is a planned view of a process device including a piezoelectrictransducer located in a process coupling.

FIG. 8 is a simplified diagram of a configuration in which apiezoelectric transducer is coupled to the process fluid at a locationremote from the process device.

DETAILED DESCRIPTION

Various prior art techniques exist which utilize mechanical vibrationsin processes for diagnostic or harvesting energy. However, thesevibrations are typically received from process components such aspiping, mounting brackets, etc rather than from directly receivingpulsations from the process fluid, for example, from process fluidcarried in a process pipe. These pressure pulsations may arise from manysources including, for example, pumps, pipe obstructions, etc. In someinstances, the internal pressure pulsations do not result in externalmechanical vibrations which are transmitted into the piping itself,brackets, or other components. Often, the maximum energy available isinside the process vessel, for example inside the process piping. In oneaspect, the present invention includes capturing this energy from theprocess and using it for diagnostics and/or energy harvesting. As usedherein, a “pressure pulsation” is any type of a change in pressure inthe process fluid. Pressure pulsations may be carried in the form ofwaves of pressure, a traveling wavefront, etc. In one configuration, thepressure pulsations may comprise a single pressure pulse and in otherconfigurations, the pressure pulsation can be a periodic or repeatingwave form, or other wave form having an extended duration.

FIG. 1 is a simplified diagram of an industrial process controllermonitoring system 10 including a process device 16 in accordance withthe present invention. As discussed in more detail below, process device10 includes a piezoelectric transducer (not shown in FIG. 1) configuredto move in response to pressure pulsations in system 10 and therebygenerate an electrical output.

Process device 16 is shown coupled to process piping 12 which isconfigured to carry a process fluid 14. A process interface element 18is configured to couple to the process and is used for input or outputto the process device 16. For example, if the process device isconfigured as a process control transmitter, interface element 18 cancomprise some type of a process variable sensor such as a pressuresensor, flow sensor, temperature sensor, etc configured to sense aprocess variable. On the other hand, if process device 16 is configuredas a process control device, interface element 18 can be, for example, avalve, a heater, a motor, a pump, etc., which is used to control theprocess. Process device 16 couples to remotely located circuitry such ascontrol room 20 over a process control loop 22. Process control loop 22is illustrated as a two wire process control loop and can comprise, forexample, a process control loop configured to operate in accordance withindustrial standards. Example industrial standards include 4-20 mAprotocols, the HART® protocol, FieldBus protocols, and others. In someembodiments, device 16 communicates using a wireless process controlloop and may or may not also couple to wired loop 22. FIG. 1 also showsa pressure pulse 72 carried in the process fluid.

FIG. 2 is a simplified cross-sectional view showing one exampleembodiment of the present invention in which process device 16 couplesto process piping through a process coupling 50 such as a flange or thelike. Field device 16 includes interface circuitry 52 which couples toprocess interface 18. When configured as a transmitter, interfacecircuitry 52 can perform initial processing and operate with a processvariable sensor. Similarly, when configured as a process controller,interface circuitry 52 is used to control the process interface 18.Field device 16 includes a microcontroller 60 which operates inaccordance with programming instructions stored in memory 62.Microcontroller 60 also couples to I/O circuitry 64 which itself couplesto process control loop 22. In some configurations, I/O circuitry 64also provides a power output which is used to power some or all of thecircuitry of process device 16.

Piezoelectric transducer 68 is mounted in a device housing 70 of theprocess device 16. Piezoelectric transducer 68 is physically coupled tothe process, either directly or indirectly through one or moreadditional components, such that pressure pulsations 72 emanating fromthe industrial process 14 are received by piezoelectric transducer 68.These pulsations cause movement of transducer 68 which results in anelectrical output signal 74 which is a function of the receivedpulsations. In the configuration of FIG. 2, piezoelectric transducer 68provides an electrical output signal 74 to an analog to digitalconverter 76. The analog to digital converter 76 receives the outputsignal 74 and provides a digitized signal 80 to the microcontroller 60.The microcontroller 60 can process the digitized signal using anydesired technique and is not limited to those discussed herein.

In one example configuration, microcontroller 60 monitors the amplitude,spectral content and/or signature (time and/or frequency) of thepulsation signal 72. The signal 72 can be compared against known signalswhich are representative of nominal operation of the process 10. Nominalsignal values such as amplitude, spectral content and/or signatures canbe stored, for example, in memory 62.

In another example configuration, certain levels or thresholds in theoutput signal 74 may indicate specific failures in the process 10 suchas a broken or failing pump or bracket. Similarly, certain frequenciesor groups of frequencies may suggest specific failures such as a failingor failed impeller. The pulsation information can also be used toprovide prognostic information related to the expected lifetimereduction in the process device 10, or other device in process 10, dueto the exposure to pulsations. If, during operation of the processdevice 16, the pulsation signal 72 varies in a predetermined manner fromthe stored nominal values, programming instructions executed bymicrocontroller 60 can be used to make a determination that some type ofevent has occurred in the process which warrants further investigation.For example, the microcontroller 60 can provide an output signalindicative of component failure or potential failure that should beinvestigated by an operator. The information can also be used for otherpurposes such as to provide an indication of operation of othercomponents in the industrial process such as a valve controller or thelike. If the process coupling 50 has become loose, the pulsation signal72 will also change. In another example, if the pulsation signal 72should suddenly decrease or even disappear completely, this can be anindication that the process 10 has improperly shut down or is in anundesirable state. Various examples of diagnostic techniques are shownin U.S. Pat. No. 6,601,005, issued Jul. 29, 2003 by Eyrurek, which isincorporated herein by reference in its entirety.

FIG. 3 is another simplified block diagram of process device 16 showinganother example configuration of the present invention. In FIG. 3,elements which are similar to those shown in FIG. 2 have retained theirnumbering. In the configuration of FIG. 3, the pulsation signal 72 isreceived by piezoelectric transducer 68. The current output signal 74from piezoelectric transducer 68 is provided to a power storagecircuitry 82. Power storage circuitry 82 can be any appropriate devicefor storing electrical power and can include, for example, an electricalcapacitor and rectifying circuitry, a battery, etc., used to storeenergy from piezoelectric transducer 68. Power storage circuitry 82provides a power output signal which can be used to power process device16. In such a configuration, I/O circuitry 64 may not be required toprovide a power output signal. Further, in some configurations processdevice 16 is configured to operate over a wireless connection and I/Ocircuitry 64 is used for wireless communication. Power storage circuitry82 can provide all of the power for process device 16, or can providesupplemental or backup power to the device 16.

In general, power from the process cannot be harvested using thistechnique unless there is kinetic energy. For example, a pressurizedvessel may contain a significant amount of potential energy. However, ifthe pressure remains constant, the energy cannot be harvested. Onesolution is to harvest energy created by process pressure noise such asdue to a water “hammer” effect, pump pulsations, etc. With the presentinvention, such energy can be harvested using a piezoelectric effect.Typical piezoelectric elements have a relatively low current output.However, given a sufficient input force, enough power may be generatedto be useful in process control devices. In various configurations, thepiezoelectric transducer can be used to harvest power from pressurepulsations in the process fluid. The piezoelectric transducer can beintegrated into a pressure sensor module or process connection tothereby eliminate external wiring. A battery capacitor or other powerstorage device, such as power storage 82 shown in FIG. 3, can beincluded in the configuration. The battery can wholly or partiallysupplement power provided by the piezoelectric transducer. Further, thepiezoelectric transducer can be used, to charge the battery when thereis sufficient excess energy. This can also extend the life of thebattery by reducing discharge. In another example configuration, acontrol signal can be applied to the piezoelectric transducer 68 frommicrocontroller 60 to thereby cause movement of the transducer 68 andprovide pressure pulsations. In such a configuration, the inducedpressure signal can be sensed by a pressure sensor of the process deviceto diagnose or verify transmitter operation. The magnitude of the signalcan also be used to provide an indication of line pressure. Although asingle piezoelectric transducer 68 is illustrated, multiple circuits canbe used.

FIG. 4 shows a bottom plan view of a pressure module 150 for use in oneembodiment of the present invention. The pressure module 150 includes anisolation diaphragm 152 for coupling to a high side of a processpressure and an isolation diaphragm 154 for coupling to a low pressureside of a process pressure. A pressure sensor, for example embodied ininterface circuitry 52 shown in FIGS. 2 and 3, can be used and arrangedto measure a differential pressure between diaphragms 152 and 154applied by process fluid. Such differential pressure can be indicative,for example, of flow rate of the process fluid. A isolation diaphragm156 can be used to couple the piezoelectric transducer 68 to the processfluid. For example, the piezoelectric transducer 68 can mount to theisolation diaphragm 156 such that movement of the isolation diaphragm156 causes movement of the piezoelectric transducer 68. This allowstransducer 68 to directly sense pulsations in the process fluid.

FIG. 5 is a side cross sectional view of module 150 showing diaphragm156 in greater detail. As illustrated in FIG. 5, the piezoelectricsensor 68 is physically coupled to diaphragm 156. The sensor 68 is shownpositioned in a cavity 170 formed in module 150. An electricalconnection carries the output 74 from transducer 68. In theconfiguration of FIG. 5, as pulsations occur in the process fluid,diaphragm 156 will move. This movement of diaphragm 156 causes aresultant movement of transducer 68 which results in an electricaloutput. As discussed above, an input signal can be applied to transducer68 resulting in movement of diaphragm 156 which induces a pulsation inthe process fluid.

FIG. 6 is a plan view of another example embodiment of the presentinvention in which the process variable transmitter is shown whichincludes a transmitter electronics housing 202 and a sensor module 204.A mounting flange 206 is used to mount the transmitter sensor module 204to piping of an industrial process. The flange 206 may, for example,include valves or the like. In the configuration of FIG. 5, thepiezoelectric transducer 68 is carried in the flange 206 and can be, forexample, coupled to the process fluid using a technique such as thatillustrated in FIG. 5 which uses the diaphragm 156. An electricalconnection 210 extends from flange 206 to the transmitter electronichousing 202 is used to couple electrical signals and/or from thetransducer 68.

FIG. 7 is a plan view of transmitter 200 configured in a similar mannerto that which is shown in FIG. 6 and the numbering has been retainedaccordingly. However, in the configuration of FIG. 7, the transmitter200 includes some type of a process coupling 220 such as a probe forsensing temperature, pressure, etc. The coupling in the configuration ofFIG. 7, the coupling 220 is illustrated as including the piezoelectrictransducer 68. The transducer 68 can be coupled to the process using anyappropriate technique, including, for example, the diaphragm 156 shownin FIG. 5.

In the configurations of FIGS. 6 and 7, the piezoelectric transducer iscarried in a “wetted” component. Such configurations may be advantageousbecause they can be repaired or upgraded in the field without alteringthe transmitter itself. Further, these configurations do not requireadditional space within the transmitter housing.

FIG. 8 shows another example configuration of the present invention inwhich the piezoelectric sensor 68 is coupled to process piping 230through a resonant pipe 232. The transducer 68 couples to a processdevice, such as those discussed above through electrical connection 234.In the configuration of FIG. 8, the piezoelectric transducer isseparated from the process device. The transducer 68 may includeelectronics to provide amplification or signal processing and can beconfigured to screw, for example into a threaded port on a vessel. Inone configuration, the transducer 68, including its associateelectronics, is between 1 to 2 inches in diameter and 1 to 2 inches inheight and appear as a pipe plug. Such a configuration is advantageousbecause it may be repaired or upgraded in the field and increases energyharvesting as the process measurement point may be different from theoptimum process noise location. The optional resonant in pipe 262 may beconfigured to take advantage of standing waves that can occur in anyclosed wave medium. For example, this configuration can be used toamplify or otherwise focus pulsations in the process fluid onto thepiezoelectric transducer 68. In the example of a resonated pipe, theequation is L=Vs/F where L is the length of the pipe, Vs is the speed ofsound and F is the frequency of the sound. In one configuration,pulsation frequencies of interest will generally be in the range of 60to 80 hertz and the length of resonant pipe 232 may be between 0.5 andone meter.

Although other configurations may be used, in one embodiment, thecircuitry may include a super capacitor to store electrical charge fromthe piezoelectric transducer. When the energy being scavenged issufficient to power the device, the scavenged energy can be used ratherthan energy from a battery. Further, when scavenged energy is stillgreater, excess charge can be stored in, for example, a super capacitor.However, if the energy generated by the transducer 68 is not sufficientto power the device, energy from a battery may be used. Thus, in such aconfiguration, the energy scavenging does not replace the battery in thedevice, but rather extends battery life.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. Although the embodiments of FIGS. 2 and 3are illustrated separately, the piezoelectric transducer 68 can be usedsimultaneously for both is diagnostics as well as power generation.

1. A process device for coupling to an industrial process for use inmonitoring or controlling the process, comprising: a device housingconfigured to physically couple to the industrial process; a processvariable sensor configured to measure a process variable; measurementcircuitry coupled to the process variable sensor having an outputrelated to the sensed process variable; a piezoelectric transducerhaving an electrical output related to pressure pulsations in theindustrial process; electrical circuitry in the housing having an inputconfigured to receive the electrical output from the piezoelectricsensor; and wherein the electrical circuitry is configured to diagnoseoperation of the industrial process based upon the electrical outputfrom the piezoelectric transducer.
 2. The apparatus of claim 1 whereinthe process device is powered with the electrical output.
 3. Theapparatus of claim 1 including an analog to digital converter having adigital output related to digitize the electrical output.
 4. Theapparatus of claim 1 including a microcontroller configured to performdiagnostics.
 5. The apparatus of claim 1 wherein the diagnostics arebased upon an amplitude of pulsations in the industrial process.
 6. Theapparatus of claim 1 wherein the diagnostics are based upon a frequencyof pulsations in the industrial process.
 7. The apparatus of claim 1wherein the diagnostics are based upon a signature in the pulsations inthe industrial process.
 8. The apparatus of claim 1 wherein theelectrical circuitry provides a diagnostic output based upon thepulsations and data stored in a memory.
 9. The apparatus of claim 1wherein the piezoelectric transducer is configured to receive a controlsignal which causes movement of the piezoelectric transducer.
 10. Theapparatus of claim 1 wherein movement of the piezoelectric transducerinduces pressure pulsations in the process fluid which are sensed by theprocess variable sensor, the electrical circuitry further configured todiagnose transmitter operation based upon the sensed pressurepulsations.
 11. The apparatus of claim 1 wherein the electricalcircuitry includes power storage circuitry configured to store powerfrom the piezoelectric transducer.
 12. The apparatus of claim 11 whereinthe power storage circuitry comprises a capacitor.
 13. The apparatus ofclaim 12 wherein the capacitor comprises a supercapacitor.
 14. Theapparatus of claim 1 wherein the piezoelectric transducer is mounted inthe housing of the process device.
 15. The apparatus of claim 1 whereinthe piezoelectric transducer is mounted in a sensor module of theprocess device.
 16. The apparatus of claim 1 wherein the piezoelectrictransducer is carried on a mounting flange used to couple the processdevice to the industrial process.
 17. The apparatus of claim 1 whereinthe piezoelectric transducer is positioned at a location which is spacedapart from the device housing.
 18. The apparatus of claim 1 wherein thepiezoelectric transducer couples to the process fluid through a resonantpipe.
 19. The apparatus of claim 1 wherein the piezoelectric transducercouples to process fluid through a diaphragm.
 20. A method for sensingpulsations in a process device coupled to an industrial process of thetype used in monitoring a process variable of industrial process, themethod comprising: physically coupling a piezoelectric transducer to theindustrial process; receiving pressure pulsations from the industrialprocess through the physical coupling; sensing a process variable with aprocess variable sensor; providing a process variable output based uponthe sensed process variable; coupling the pressure pulsations to thepiezoelectric transducer and providing an electrical output from thepiezoelectric transducer in response to the pressure pulsations;providing the electrical output to circuitry of the process device; anddiagnosing operation of the industrial process based upon the electricaloutput.
 21. The method of claim 20 including powering the electricalcircuitry with the electrical output.
 22. The method of claim 20including digitizing the electrical output.
 23. The method of claim 20wherein the diagnosing is based upon an amplitude of pulsations in theindustrial process.
 24. The method of claim 20 wherein the diagnosing isbased upon a frequency of pulsations in the industrial process.
 25. Themethod of claim 20 wherein the diagnosing is based upon a signature inthe pulsations in the industrial process.
 26. The method of claim 20including providing a diagnostic output based upon the pulsations anddata stored in a memory.
 27. The method of claim 20 including providinga control signal to the piezoelectric transducer which causes movementof the piezoelectric transducer.
 28. The method of claim 27 wherein themovement of the piezoelectric transducer induces pressure pulsations inthe process fluid and sensing the pressure pulsations with the processvariable sensor, the method further including diagnosing transmitteroperation based upon the sensed pressure pulsations.
 29. The method ofclaim 20 wherein the piezoelectric transducer is mounted in the housingof the process device.
 30. The method of claim 20 wherein thepiezoelectric transducer is mounted in a sensor module of the processdevice.
 31. The method of claim 20 wherein the piezoelectric transduceris carried on a mounting flange used to couple the process device to theindustrial process.
 32. The method of claim 20 wherein the piezoelectrictransducer is positioned at a location which is spaced apart from thedevice housing.
 33. The method of claim 20 wherein the piezoelectrictransducer couples to process fluid through a resonant pipe.
 34. Themethod of claim 20 wherein the piezoelectric transducer couples toprocess fluid through a diaphragm.